1. Field of the Invention
This invention relates to a transport system for feeding articles from station to station in a continuous manufacturing line and warehouse. More particularly, it relates to an apparatus and method for temporarily retaining articles midway the transport system.
2. Prior Art
A continuous manufacturing system includes a transport line in the form of a roller conveyor for feeding stock items or intermediate articles from station to station for processing and finally feeding finished articles to a packaging station or a shipping outlet. Midway the transport line, there sometimes arises a need to temporarily retain the stock items, intermediate articles or finished articles for a relatively short time. For example, in a process for manufacturing edible items including bread, cakes, noodles, and paste items, stock powder and suitable agents are mixed. It is often desired to retain such a mixture for some time at room temperature for aging for allowing the material to gain some drape, texture or body. When the material is heated as by baking, it is also desired to allow the material to cool down at room temperature. In such a situation, if one attempts to perform aging or cooling while the articles are being fed along the transport line, the line must be extremely extended. If the articles are removed off the line for aging or cooling purpose, then the process becomes discontinuous, resulting in less efficient operation. It is, therefore, desirable to temporarily retain the articles midway the transport line for aging or cooling. In another situation where there is a difference in processing speed between upstream and downstream stations, it is also desirable to temporarily retain articles midway the transport line between these stations. In a still further situation where articles are continuously fed along a transport line from within a warehouse to a shipping exit, if shipping is intermittent, it is desirable to temporarily retain articles midway the transport line.
Exemplary apparatus for temporarily retaining and storing articles midway a transport line are disclosed in Japanese Patent Application Kokai No. 225210/1990 and Japanese Utility Model Application Kokai No. 132008/1990 as comprising two multi-stage racks arranged in a transport line in a conveyance direction whereby articles being conveyed are sequentially loaded in the multi-stage racks and fed back to the transport line.
These apparatus have a satisfactory function of temporarily retaining and storing articles midway the transport line, but require a relatively complex and expensive mechanism for loading articles in the multi-stage racks. Because of the complex mechanism, maintenance is rather difficult.
Therefore, an object of the present invention is to provide an apparatus of simple, inexpensive construction for temporarily retaining articles midway a transport line and a retaining method using the apparatus.
An article retention apparatus for use in a transport system according to the present invention includes a conveyor unit having a conveying surface for supporting and conveying an article horizontally. A plurality of rack units each have support means on which an article rests horizontally. Suspension means is provided for suspending the plurality of rack units in a vertically spaced apart relationship while keeping the rack units horizontal. Drive means is provided for moving up and down the suspension means. The conveyor unit and the plurality of rack units are configured such that the rack units may be moved above and below the conveying surface of the conveyor unit without interference between the conveying surface of the conveyor unit and the support means of the rack units.
Preferably the suspension means includes generally flexible strips or chains and the plurality of rack units are attached to the strips or chains at predetermined intervals.
In one preferred embodiment, the conveyor unit comprises a roller conveyor unit having a plurality of rollers arranged in a horizontal plane. The rollers at their top define the conveying surface. More preferably, each rack unit is a ladder-shaped rack and the conveyor unit has a plurality of spaced apart rollers, the crosspieces of the ladder-shaped rack and the rollers are alternately arranged in a non-contact interdigitating relationship.
In another preferred embodiment, the conveyor unit comprises at least one belt conveyor unit having an endless belt. The belt presents a horizontal upper surface defining the conveying surface.
Using the article retention apparatus, articles are retained midway a transport system by placing the plurality of rack units on standby in a stack at a position below the conveying surface of the conveyor unit. An article is fed from the transport system to the conveyor unit so that the article rests on the conveying surface. The suspension means is lifted upward for moving upward the rack unit of the uppermost stage to emerge above the conveying surface, thereby transferring the article from the conveying surface to the support means of the rack unit. The suspension means is lifted in increment each time when a new article is fed and rested on the conveying surface, for moving upward the rack unit of the next lower stage to emerge above the conveying surface, thereby transferring the article from the conveying surface to the support means of the rack unit. The respective rack units retain the articles at spaced apart positions above the conveying surface for a desired time. Thereafter, the suspension means is moved downward in increment until each of the rack units is moved below the conveying surface of the conveyor unit, thereby transferring the article from the support means of the rack unit to the conveying surface. The articles are then discharged from the conveyor unit to the transport system.
In the article retaining apparatus of the invention, a plurality of rack units each having support means on which an article rests horizontally can be suspended by suspension members in a vertically spaced apart relationship while the rack units remain horizontal. The conveyor unit and the plurality of rack units are configured such that the rack units may be moved to positions above and below the conveying surface of the conveyor unit (which is the roller plane in the case of a roller conveyor and the belt surface in the case of a belt conveyor) without interference between the conveying surface of the conveyor unit and the support means of the rack units. Therefore, in retaining an article which has been fed to the conveying surface of the conveyor unit from the transport system, the rack unit of the uppermost stage among a plurality of rack units which have been placed on standby at a position below the conveying surface is lifted upward by the suspension members to emerge above the conveying surface whereby the article on the conveying surface is transferred to the support means of the rack unit. That is, the article rests on the rack unit independent of the conveyor unit. Rack units of subsequent lower stages are then sequentially lifted from the standby position to emerge above the conveying surface to thereby sequentially transfer the articles from the conveying surface to the support means of the rack units. The articles are stored on the respective rack units which are lifted above the conveyor unit.
Transport of the articles which have been stored as mentioned above is restarted by moving down the suspension members to cause the rack units to descend from above to below the conveying surface of the roller conveyor unit. On passage of each rack unit across the conveying surface, the article on the rack unit is left on the conveying surface and then horizontally fed by the conveyor unit along its the conveying surface. By sequentially moving the rack units below the conveying surface, the articles are fed from the rack units back to the conveying surface of the conveyor unit and then horizontally fed until they are fed back to the transport system.
In the preferred embodiment wherein the suspension members are chains or strips which are flexible as a whole, the chains can flex between the rack units, which allows the rack units, when they are on standby below the conveying surface, to be closely stacked on a stationary surface below the conveying surface.